1. Field of the Invention
The present invention generally relates to electron beam pumped lasers, and particularly to electron beam pumped lasers such as those that provide a light source for projection television.
2. Description of Related Art
Electron beam-pumped vertical cavity surface emitting lasers, known as “eVCSELs,” can be used for a variety of applications including but not limited to projection televisions and high-power laser-light sources. An eVCSEL requires an electron source that can include a vacuum tube and an electron gun or an array of field emitters. The electron source generates an electron beam that is deflected and focused by magnetic fields to impinge upon a desired location on a laser faceplate.
The faceplate of an eVCSEL includes a laser structure instead of the conventional phosphors; therefore the faceplate emits laser light in response to electron beam pumping.
More particularly, the faceplate of a typical eVCSEL comprises a laser structure of semiconductor materials that forms the gain medium, is sandwiched between a highly reflective mirror and a partially reflective mirror in which a scanning electron beam bombards either one of the reflective mirrors. These mirrors may include, for example, a conventional dielectric stack of quarter-wave alternating layers of Al2O3 and TiO2 with or without a metal layer in order to achieve a partially and highly reflective mirror. These mirrors could also be made as part of a monolithic structure where the mirrors are deposited during the same process as the gain medium.
To provide a light source for proposed visual displays (and particularly for large screen displays for consumer and/or commercial use), one or more eVCSELs can generate and modulate red, green, and blue laser light beams, and the beams are combined to make a full-color image. More particularly, in a typical display system, one eVCSEL generates red light, another eVCSEL generates green light, and a third eVCSEL generates blue light. One embodiment of a light source for projection television is disclosed in U.S. Pat. No. 7,309,953, issued Dec. 18, 2007, and entitled “Electron Beam Pumped Laser Light Source for Projection Televisions,” which is herein incorporated by reference in its entirety. Another light source is disclosed in U.S. patent application Ser. No. 10/981,075, filed Nov. 3, 2004, and published on May 26, 2005, as Publication No. US2005-0110386A, entitled “Laser Cathode Ray Tube,” which is herein incorporated by reference in its entirety.